Removing peanut allergens by tannic acid

Tannic acid (TA) forms insoluble complexes with proteins. The aims here were to remove major peanut allergens as insoluble TA complexes and determine if they would dissociate and release the allergens at pH 2 and 8 (gut pH). Release of the allergens in the gut could lead to absorption and consequently an allergic reaction. TA (0.25, 0.5, 1, and 2 mg/ml) was added to a peanut butter extract (5 mg/ml; pH 7.2), stirred, and centrifuged. The precipitates were then suspended in buffer at pH 2, centrifuged, re-suspended at pH 8, and centrifuged. Supernatants from each step were analysed by SDS–PAGE, ELISA, and Western blots. The effect of NaCl (1 M) on complexes was also determined. Results showed that complexes formed at a TA concentration >0.5 mg/ml did not release major peanut allergens at pH 2 and 8, regardless of 1 M NaCl being present or not. IgE binding of the extracts was reduced substantially, especially at a TA concentration of 1–2 mg/ml. Animal or clinical studies are still needed before TA can find an application in the development of low-allergen peanut products/beverages or the removal of peanut allergens due to accidental ingestion.     

Effect of some operating variables on the microstructure and physical properties of a novel Kefir formulation

In this work, the rheological and textural properties, water-holding capacity (WHC), syneresis, and microstructure of a novel formulation of Kefir were studied by varying the incubation time and temperature, as well as the ratio of peanut-milk and skimmed-milk. Generally, all the experimental responses resulted to be significantly affected (p < 0.05) by all dependent variables examined. Kefir WHC was not significantly influenced (p > 0.05) by the fermentation temperature.     

Biosensors for monitoring the isothermal breakdown kinetics of peanut oil heated at 180 °C. Comparison with results obtained for extra virgin olive oil

The present research was devoted to studying the kinetics of the artificial rancidification of peanut oil (PO) when a sample of this oil was isothermally heated at 180 °C in an air stream. The formation of radical species due to heating was evaluated using a radical index whose value was determined using a biosensor method based on a superoxide dismutase (SOD), while the increasing toxicity was monitored using a suitable toxicity measuring probe based on the Clark electrode and immobilized yeast cells.     

Effect of Industrial Chemical Refining on the Physicochemical Properties and the Bioactive Minor Components of Peanut Oil

The effect of the industrial chemical refining process on the physicochemical properties, fatty acid composition, and bioactive minor components of peanut oil was studied. The results showed that the moisture and volatile matter content, acid value, peroxide value, and p‐anisidine value were significantly changed (P < 0.05) after the complete refining process. No significant variation (P > 0.05) in the iodine value was observed among all the peanut oil samples. Similar changes were observed in the DPPH radical scavenging activity and the total tocol content during chemical refining. In addition, chemical refining did not have much effect on the fatty acid composition, except for certain changes of several individual fatty acids. Moreover, the chemical refining resulted in 23.6, 23.1, and 9.5 % losses of squalene, total phytosterols, and total tocols (α, β, γ, δ‐tocopherols and α, β, γ, δ‐tocotrienols), respectively. The degumming–neutralization step caused the greatest overall reduction of these bioactive minor components. However, the concentrations of α‐tocotrienol and γ‐tocotrienol increased after full refining. Furthermore, chemical refining slightly changed the relative proportions of individual phytosterols and individual tocols.     

Influence of ultrasonic treatment on the structure and emulsifying properties of peanut protein isolate

Effects of ultrasonic treatment on emulsifying properties and structure of peanut protein isolate (PPI) were evaluated by analysis of particle size distribution, protein surface hydrophobicity, SDS-PAGE, circular dichroism spectra and environmental scanning electron microscopy. The emulsifying properties of the PPI were found to be improved by ultrasonic treatment. The mean particle size decreased from 474.7 nm to 255.8 nm while the molecular weight remained unaffected. The results of intrinsic fluorescence spectroscopy and surface hydrophobicity indicated that ultrasonic treatment induced tertiary structural changes of the proteins in PPI. Emulsifying activity index and emulsion stability index were found to be correlated fairly well with surface hydrophobicity (H₀) (r = 0.712 and r = 0.668, respectively).     

Enzymatic treatment of peanut kernels to reduce allergen levels

This study investigated the use of enzymatic treatment to reduce peanut allergens in peanut kernels as affected by processing conditions. Two major peanut allergens, Ara h 1 and Ara h 2, were used as indicators of process effectiveness. Enzymatic treatment effectively reduced Ara h 1 and Ara h 2 in roasted peanut kernels by up to 100% under optimal conditions. For instance, treatment of roasted peanut kernels with α-chymotrypsin and trypsin for 1–3 h significantly increased the solubility of peanut protein while reducing Ara h 1 and Ara h 2 in peanut kernel extracts by 100% and 98%, respectively, based on ELISA readings. Ara h 1 and Ara h 2 levels in peanut protein extracts were inversely correlated with protein solubility in roasted peanut. Blanching of kernels enhanced the effectiveness of enzyme treatment in roasted peanuts but not in raw peanuts. The optimal concentration of enzyme was determined by response surface to be in the range of 0.1–0.2%. No consistent results were obtained for raw peanut kernels since Ara h 1 and Ara h 2 increased in peanut protein extracts under some treatment conditions and decreased in others.     

Effect of denaturation during extraction on the conformational and functional properties of peanut protein isolate

Peanut protein isolate (PPI) was extracted by alkali dissolution and acid precipitation from defatted peanut flour. The effects of extraction conditions on the denaturation and functional properties of PPI were investigated. In comparison with native peanut protein (NPP) which was extracted by ammonium sulfate, the PPI extracted by alkali dissolution and acid precipitation had a higher extent of denaturation. Arachin was affected more easily by the extraction process than conarachin and led to a noticeable decrease of thermal stability of PPI. PPI contained much lower sulfhydryl and disulfide bond contents than NPP. The analyses of intrinsic fluorescence spectra indicated a more compacted tertiary conformation of NPP than PPI. Extraction process influenced the functional properties of PPI, such as protein solubility, emulsifying activity index and foaming capacity. The relatively poor functional properties of PPI might be associated with protein denaturation/unfolding and subsequent protein aggregation.

Industrial relevance

Peanut is an important oilseed crop and a well-accepted food. After oil production through thermal treatment, the defatted peanut flour is the main byproduct, which possesses a large amount of proteins. However, due to the low extraction yield and poor functional properties of these proteins, they are not well utilised in industry till now. In this work, peanut proteins were extracted by two techniques. The results indicated that extraction technique could significantly modify the functional properties of peanut proteins. Therefore, this work is helpful for industrial utilisation of peanut proteins.     

流式细胞仪检测铝胁迫诱导的花生悬浮细胞程序性死亡

以耐铝品种99-1507和铝敏感品种中花2号为材料,应用荧光显微镜和流式细胞仪研究铝对悬浮细胞活性及其线粒体生理的影响,并检测悬浮细胞程序性死亡率。结果表明：铝处理12h后,随着铝浓度增加,悬浮细胞FDA（Fluorescein diacetate）荧光信号逐渐减弱,PI（Propidium Iodide）荧光信号增强,细胞活性下降;线粒体超氧阴离子含量和H202含量随着铝浓度的增加逐渐上升;线粒体膜电位（△ψm）随着铝浓度增加逐渐下降,中花2号下降幅度大于99-1507。501μmol／L及其以上浓度的铝可以显著诱导花生悬浮细胞程序性死亡,铝浓度越高死亡细胞数量越多,同等浓度铝处理下中花2号细胞死亡率高于99-1507,差异达到显著水平。应用流式细胞仪能够准确地检测悬浮细胞程序性死亡的发生情况,细胞程序性死亡率与花生品种的耐铝性呈负相关关系。     

Enzymatic hydrolysis and their effects on conformational and functional properties of peanut protein isolate

The effects of limited enzymatic hydrolysis by Alcalase on the conformational and functional properties of peanut (Arachis hypogaea L.) protein isolate (PPI) were investigated. Acid subunits of arachin were most susceptible to Alcalase hydrolysis, followed by conarachin and the basic subunits of arachin. Enzymatic hydrolysis increased the thermal stability of arachin and led to a sharp increase in the number of disulphide bonds with a decrease of the sulphydryl group in PPI hydrolysates in comparison with PPI. The analysis of intrinsic fluorescence spectra indicated a more moveable tertiary conformation of PPI hydrolysates than PPI. The limited emzymatic hydrolysis improved the functional properties of PPI, such as protein solubility and gel-forming ability, but impaired the emulsifying activity index.     

Analysis of Peanut Using Near-Infrared Spectroscopy and Gas Chromatography–Mass Spectrometry: Correlation of Chemical Components and Volatile Compounds

Peanut contains protein, oil, oleic acid, and linoleic acid its flavor is largely determined by pyrazine and aldehyde compounds. Both nutritional value and flavor are standards for measuring peanut quality. In this report, the contents of protein, oil, oleic acid, and linoleic acid were determined using near-infrared reflectance spectroscopy, and flavor compounds were identified using headspace solid-phase microextraction combined with gas chromatography–mass spectrometry in 12 different peanut cultivars. Our results showed that the content of oleic acid in raw peanut ranged from 35.69 to 82.79 g/100 g oil and the linoleic acid content ranged from 2.92 to 44.19 g/100 g oil, with high coefficients of variation. The coefficients of variation of protein and oil were lower, with content of 26.97–33.07 g/100 g raw materials and 45.53–55.53 g/100 g raw materials, respectively. Overall, 14 volatile components were isolated and identified, among which pyrazine and aldehyde compounds were the major aroma components in 12 different peanut cultivars.. Based on these results, peanuts with high protein content have high linoleic oil levels but low oleic oil levels, and roasted peanuts have a high content of pyrazines but low content of aldehydes. The results of this study will enable manufacturers to develop simple tests that predict the flavor of roasted peanuts based on their composition.